Simple Query Question - How do I return the Last 3 records of a Table?

Question

Question.
For example, I have a table that has 50 records.
How do I, specify in SQL to only return the last 3 records of the table.
Select a.* from table a where ????

Answer 1

I was just trying to show an example to a friend on
how something like this would work and if it was even possible. But it won't work. Here's a simple example:
SQL> create table emp
  2  (id)
  3  as
  4  select object_id
  5  from   all_objects
  6  order  by object_id;
Table created.
SQL> select *
  2  from  (select rownum rn
  3               ,b.*
  4         from   emp b)
  5  where  rn > ( select (max(rownum) - 3)
  6                from    emp)
  7  ;
        RN         ID
     40830      55891
     40831      55892
     40832      55893So far, so good. These are the "last 3" rows inserted. Now delete a bunch of rows and insert 3 new ones:
SQL> delete emp where id < 40000;
33423 rows deleted.
SQL> commit;
Commit complete.
SQL> insert into emp values (60000);
1 row created.
SQL> insert into emp values (60001);
1 row created.
SQL> insert into emp values (60002);
1 row created.
SQL> commit;
Commit complete.
SQL> select *
  2  from  (select rownum rn
  3               ,b.*
  4         from   emp b)
  5  where  rn > ( select (max(rownum) - 3)
  6                from    emp)
  7  ;
        RN         ID
      7410      55891
      7411      55892
      7412      55893Here's the problem. Even though the "last 3 rows" are 60000 - 60002, I still get the same ones as the first query.